Carrier-wave transmission



Aug. 20, 1929. 5 JAMMER 1,724,938

CARRIER WA VE TRANSIISSION Original Filed July 25. 1923 Channel 5 .3 4%Channel 2 M. TBF. TC.

Channel I A, DM, RBI

I RC. ,5: R, HBF

lnrenfor: Jamb 5 Jammer by z. v/QM- Alf}! Patented Aug. 20, 1929.

UNITED STATES PATENT OFFICE.

.mcoia a. same, or SYDNEY, new scorn-wanna, AUSTRALIA, assreuoa TOWESTERN ELECTRIC COMPANY, INCORPORATED,

romnon on NEW ou.

01' NEW YORK, N. Y., A COB- OABRIEB-WAVE TRANSMISSION.

Original application filed July 25, 1923, Serial No. 658,629. Dividedand this application filed November 20, 1928. Serial No. 149,779. I

This invention relates to carrier wave transmission, and is a divisionof application, Serial No. 653,629, filed July 25, 1923, patentedDecember 21-, 1926, No. 1,611,350.

5 An object of the invention is to increase the number of signalingchannels in a multiplex carrier signaling system within a g1venfrequency range.

Another object of the invention is to provide a novel method of andapparatus. for

transmitting telephone and telegraph signals simultaneously on the samecarrier wave.

According to this invention, a multiplex carrier Wave telephone systemhas associated with one or more channels thereof telegraph transmittersfor changing the magnitude of the carrier current in the telephonechannels and receiving apparatus to enable the telegraph signals to bereceived Without afiecting the operation of the carrier telephoneapparatus.

In the drawings; Fig. 1 is a diagrammatic illustration of a multiplexcarrier telephone and telegraph system embodying the invention;

Fig. 2 shows curves representing the magnitude and form of the carrierand voice side band waves in the system of Fig. 1 and Fig. 3 shows theoperating characteristics of the rectifiers employed inthe system of-Fig. 1. g

In Fig. 1 there is illustrated the west terminal of a multiplex carriertelephone .and telegraph system connected to the high frequencytransmission line ML. The usual east terminal, which is identical to thewest terminal shown in the drawing, is omitted for the sake ofsimplifying the showing.

40 The telephone channels employ different carrier frequencies, thoseused for'transmission in one direction being grouped in a differentfrequency range from those employed for transmission in the oppositedi-' rection.

The multiplex carrier telephone and telegraph system illustrated hasthree or more telephone channels upon each of which may be superimposeda telegraph channel arranged for two-wa operation, the teleaph channelsemp oyin the same carrier equencies. Since the c annels are alike exceptfor the constants of some of the apparatus thereof, due to the differentfrequencies employed, it will be unnecessary to The transmitting channelTC includes a modulator M and a transmitting band filter TBF Themodulator-M may be of any well-known t pe such, for example, as theelectronic va ve modulator of the threeelectrode type disclosed in Fig.42 of an article entitled Carrier current telephony and telegraphy byMessrs. Colpitts and Blackwell, published in the Transactions of theAmerican Institute of Electrical Engineers, vol. 40, 1921. Carriercurrent of the frequency assigned to this channel is supplied to themodulator M from a high frequency source 0 The transmitting band filterTBF may be of the type disclosed in U. S. patents to Campbell, Nos.1,227,113 and 1,227,114, issued May 22, 1917. This band filter isdesigned to pass currents of the carrier fre-' quency assigned to thischannel and currents of frequencies within either the upper or lowerside band thereof and to suppress currents of all other frequencies.

. In order that the telegraph channel may be superimposed upon thistelephone channel, there is associated therewith a telegraphtransmitting key 6 which, during the operation thereof, is adapted tointermittently shunt an impedance element 7, which may take the form ofa non-inductive resistance, across the -leads from the source of highfrequency current 0 Thus, during nately reduced from and restored toitsv normal Value. Consequently, the telephone signal modulated cah'iercurrent output filter LBF, a high frequency band filter HBF, a rectifierR and a telegraph receiving relay 8 which controls the usual telegraphsounder 9.

The receiving band filter -RBF is of the type disclosed in the Campbellpatents, su

pra. It is designed to pass currents of the carrier frequency assignedto this channel and of the frequencies within either the upper or lowerside band thereof and to suppress currents of all other frequencies.

The demodulator DM and the amplifier A may be of any well-known typessuch, for example, as those disclosed inFig. 42 of the Colpitts andBlackwell article, supra.

The low frequency band filter LB-F is of the type disclosed insaid'Campbell patents. It is designed to pass .currents within the voicefrequency range between about 200 and 2000' cycles frequency and tosuppress currents of higher frequencies as well asthe telegraph signalsbelow 200 cycles. The high frequency band filter HBF is designed to passcurrents of the carrier frequency as signed to this channel and offrequencies within both orone of the telegraph side bands and tosuppress currents of allother frequencies. Thus, these. two filtersseparate the received telephone and telegraph si als. v

lghe rectifier R may be of any well-known t e such, for example, as thatdisclosed in Fig. 42 of the Golpitts and Blackwell article,

su ra.

he operation of the system, in so far as transmission and reception oftelephone signals are concerned, is well known. Therefore, nodescription thereof will be given. a

Fig. 2 shows a set of curves representing the magnitudes of thetransmitted waves of different fre uencies. Curve 'A shows the'magnitude 0 the carrier waves when the telegraph key 6 is open, curve Bthe magnitude of the carrier waves when the telegraph key is closed, andcurve C the magnitude of the voice side band waves.

Fi 3 shows the characteristic curve of the rectifier R The curve D isplotted with input voltages E as abscissae against rectified currents L;as ordinates. When the telegraph key 6 is open, the input voltage aimpressed upon the rectifier causes rectified current of magnitude :1:to flow; and when the telegraph key is closed, the input voltage I) tudeof the carrier wave. 1

impressed upon the rectifier causes rectified current of magnitude Y tofiow.

The operation of the telegraph channel superimposed upon the telephonechannel and employing the same carrier frequency may be explainedby-reference to Fig. 8. When the telegraph key 6 is open, the normalamount of carrier current is flowing to the line and the amount ofrectified current through the telegraph receiving relay 8 at the distantstation is sufiicient to hold its contact-closed, thereby maintainingthe circuit of the sounder 9 closed. When the telegraph key 6 is closed,the amount of carrier fed to the line is reduced as indicated in Fig.2,and the amount of rectified current through the receiving relay 8 at thedistant station is reduced to such an extent that the relay can nolonger hold up its armature. The circuit of the sounder 9 is thereforeopened. When the telegraph key 6 is again the difference between theamplitudes of.

the carrier frequencies when the telegraph key is open and closed.Consequently, there is no interference between the simultaneouslytransmitted telephone and telegraph signals. The invention set forthherein is, of course, susceptible of. various other modifications andadaptations not specifically shown but included within the scope of theappended claims. For example, the invention is not limited to telephonetransmission inv the narrow sense of that term, since the variable waveswith which the carrier current is modulated may represent somethingother than speech such as the characteristics of a picture to beelectrically transmitted. What is claimed is:

1. In a carrier wave transmission system,

varied in accordance with signals of one character between definitefixed limits to produce signals of another'character WhlCh aredistinguished according to the ampli- 2. The method of transmitt' gtelegraph signals and speech or similar signals simultaneously whichcomprises varying the amplitude of carrier waves in accordance with thespeech or similar signal waves and changing the amplitude of saidcarrier waves modulated with the signal waves between definite fixedvalues in accordance with the telegraph signals to produce signals thatare distinguished by the change in amplitude of the carrier wave.

3. In a carrier wave transmission system, the method of signaling whichcomprises transmitting a plurality of carrier waves of differentfrequencies each modulated in ac cordance with speech, varying theamplitude of each of said carrier waves to transmit signals ofanotherCharacter, and reproducing said last mentioned signals at a receivingstation in accordance with the amplitude of the carrier wave.

4. A carrier wave transmission system comprising a source of carrierwaves, means for slowly varying the amplitude of waves f1 Jm said sourceto transmit signals of one character, means for simultaneously varyingthe amplitude of waves from said source between definite fixed limits totransmit signals of another character, and means controlled by theamplitude of the carrier wave for reproducing said last mentionedsignals at a receiving station.

5. A carrier wave transmission system comprising a source of sustainedcarrier waves at the transmitting terminal, means for modulating wavesfrom said source to transmit signals of slowly varying character, meansfor simultaneously abruptly varying the amplitude of waves from saidsource to transmit signals of another character, means at the receivingterminal for combining said modulated waves with waves of carrierfrequency to derive said first mentioned signals, the means forseparately detecting said second mentioned signals.

6. A carrier wave transmission system comprising means for transmittinga plurality of carrier waves of different frequencies each modulated inaccordance with speech, means for causing avariation in the amplitude ofeach of said modulated carrier waves to transmit telegraph signals,means for detecting the speech components of said waves, and means forseparately detecting said telegraph signals.

7. A carrier wave transmission system comprising a source of sustained.carrier waves, means for modulating waves from said source in accordancewith signal waves,-

and means for simultaneously causing a re-, duction in the amplitude ofthe modulated carrier wave to transmit telegraph spacing signals.

8. A carrier wave telephone and telegraph transmission system comprisinga source of sustained carrier waves, means for modulating waves fromsaid source in accordance with telephone signal waves, and means forreducing the amplitude of the carrier waves from said source supplied tosaid modulating means so as to transmit telegraph spacing signals whichare distinguished according to the amplitude of the carrier waves.

9. A carrier wave transmission system comprising a source of sustainedcarrier waves, a modulator for modulating waves from said source inaccordange with signal waves, an impedance, and means for intermittentlyconnecting the impedance in shunt with said carrier frequency source tointermittently decrease the amplitude of the carrier wave currents inaccordance with tele graph signals.

10. A carrier wave transmission system comprising a source of sustainedcarrier waves, a modulator, means for impressing waves from said carriersource upon said modulator, a source of low frequency signal waves,means for impressing waves from said last mentioned source upon saidmodulator, and means for abruptly varying the magnitude of the carrierwave as supplied to said modulator in accordance with a signal.

11. A multiplex carrier telephone and telegraph system comprising a highfrequency transmission line over which a plurality of high frequencywaves, each modulated in accordance with telephone and telegraph signalsare to be transmitted, a plurality of transmitting channels connected tothe line and each including modulating means for transmitting adifferent wave modulated in accordance with telephone signals, selectivemeans connecting the transmitting channels to the line and preventinginterference between the channels, and means associated with eachtransmitting channel for changing the amplitude of the carrier wave ofthe frequency assigned thereto and modulated with the telephone signalsto transmit telegraph signals.

12. A carrier telephone and telegraph system comprising a high frequencytransmission line over which a high frequency wave modulated inaccordance with telephone and telegraph signals is to be transmitted, attransmitting channel connected to the line and including modulatingmeans for transmitting carrier waves modulated in accordance withtelephone signals, means associated with the transmitting channel forchanging the amplitude of the modulated carrier wave to transmittelegraph signals, a. receiving channel connected to the line,demodulating means in the receiving channel, and means associated withthe demodulator to selectively receive the transmitted telephone andtelegraph signals.

In witness whereof, I hereunto subscribe my name this 11th day ofOctober A. D.,

,JACOB S. JALfllER.

